MAP Sensor

[CowardlyDawg]

My SES light has been on for the past few days, I checked the code, I got two diff codes

Code 33 - MAP sensor
(3 flashes, pause, 3 flashes)

Check the vacuum hoses from the MAP sensor. Check the electrical connections at the ECM. Replace the MAP sensor

and

Code 34 - Vacuum sensor or MAP sensor
(3 flashes, pause, 4 flashes)

Code 34 will set when the signal voltage from the MAP sensor is too low. Instead the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery. Replace the MAP sensor.

I replaced the MAP sensor, And i noticed it ran a little better, Less hesitation, but the light is still on and im still getting the code, Is there a way to reset it? When i have the truck off and turn it back on the light is off untill i drive about a half mile or so. Then its back on and i get the same two codes.

Also, since not many people know what the codes mean
http://www.montecarloss.com/SSThunder/gmcodes.html
There you go

Also its an 87 S10 2.8 4x4

[CowardlyDawg]

Bump

After driving around this morning the code didnt come up for about 5.5 Miles, Still Code 33 and 34, But its a new MAP Sensor.

And yes i have disconnected the negative terminal on the batt.

[Tink]

It seems odd to me that you are getting both codes... high vacuum and low vacuum... maybe it is a ground issue?

There is a way to test the MAP sensor:
Check the reference voltage supply at pin C of the MAP sensor (gray wire typically). Measure voltage between pin A (ground) and Pin C (+5 V ref). It should be right around 5 V. With Key on engine off the MAP voltage (Pin B, light green wire typically) should read around 4.8 to 4.9 volts. If it reads the same as pin C the sensor is probably is bad. Also check ground reference pin A. With everything off, measure resistance between Pin A and electrical ground. It should be fractional...

Another functional check – with engine idling MAP output voltage (depending on idle vacuum) should be in the neighborhood of 1.2 to 2.0 volts. If it is stuck at 5 volts check grounds.

Also... with engine idling check and see if you have vacuum at the MAP sensor - disconnect vacuum hose right at the MAP sensor.

[CowardlyDawg]

There is def vaccum to the MAP, ive checked it and when the vaccumm line is disconnected it stalls out, if it dont stall out it runs lk crap.

Ill check the voltages when i get back home.

[CowardlyDawg]

Now i am only getting code 33.

[Tink]

Do you have any other problems? Unstable idle? Miss fire? Running rich? Have you checked for vacuum leaks elsewhere since it is giving you the low vacuum code?

[CowardlyDawg]

Do you have any other problems? Unstable idle? Miss fire? Running rich? Have you checked for vacuum leaks elsewhere since it is giving you the low vacuum code?

I had missfire, so i changed all plugs and wires, By the way to everyone reading this, ACCEL SPARK PLUG WIRES...SUCK!. So i got new wires and that fixed my missfire, It seems to be running just right, and im in hte process of checking for vacuum leaks now. The only one that i know of is the throttlebody gasket, which i havent replaced yet.

[CowardlyDawg]

Now im only getting the issue every now and then, im thinking its a bad ground. I notice when the SES light is not throwing a code 33 it runs great, when it does it ends up being sluggish, Ground issue or a bad MAP?

[Tink]

Sounds like a bad ground or short to me... did you replace the throttle body gasket yet?

[CowardlyDawg]

Sounds like a bad ground or short to me... did you replace the throttle body gasket yet?

Not yet been waitin on it to dry up, I was gonna do it friday but it was rainin, and it looks like its gonna rain all day today, so maybe tuesday ill do it when its not rainin and the ground is dry.

[Tink]

Understand that... damn rain. I need to try to get the Little Blue truck running, but not today with the rain... and it is sitting in a freakin mud pit it seems.

[03lances]

Sup guys so thought I would tag on here since I am having the same issue here is a copy from another post of mine:


Hey guys so I need some technical info from ya. My 1996 s10 2.2L has ran like dirt for awhile now. I have changed plugs, wires, fuel filter, air filter, coolant temp sensor, cleaned IAC. Everything I did helped some but still very badly needs help. I have a scanner and watching the load value and map sensor it is giving me a load value of 70 at idle :confused: this doesnt seem right to me. It also registers around 26-27 inhg from the map at idle. Can anyone tell me if this is even close to being right? Seems way off to me and I will also get a code after awhile of system too rich.

Any ideas would be wonderful. Also I checked the misfire history on the cylinders and 2+3 had like almost 500 each!!!! and on 1+4 one was really low like 10 and the other 0

I will add one final thing. Everytime without change the truck will start up one crank cold. Then even if you only run it for like 5 mins shut it off and go to restart it, it WILL NOT even fire without pumping the pedal, it will crank until your blue in the face like its not getting spark (although it is I know its some fuel issue since you just tap the gas a little) then it will stumble back to its crappy idle again.